Forming methods for metal components include superplastic forming and hot forming of components. Typically, a metal die, such as a stainless steel die, is first treated such that an oxide layer, e.g., a nickel oxide layer, is formed on its working surface. A lubricant is sprayed on or otherwise applied over the oxide layer of the die. The metal die is then heated, either alone or together with the metal to be formed, and once the desired temperature is achieved, the metal is formed against the die, e.g., using a compressed gas, to form the component. After a number of components have been formed, the lubricant becomes baked onto the die, and must occasionally be removed and reapplied, while preserving the oxide layer underneath, before additional components may be formed with the die.
Typically, the baked-on lubricant is removed manually. The operator uses e.g. a pneumatic rotary tool and an abrasive pad to grind away the baked-on lubricant. However, this cleaning process is tedious, time consuming, and may remove or disrupt the beneficial oxide layer on the working surface of the die.
FIG. 1 is a schematic diagram of a component-forming system 100. The component-forming system 100 includes a die 102, a lower platen 104, an upper platen 106, and a gas inlet 108. The component-forming system 100 may be a superplastic-forming system or a hot-forming system.
The die 102 is fabricated from a rigid, temperature-resistant material. In embodiments, the die 102 is a superplastic forming die or a hot-forming die. The die 102 includes a working surface 110 that is shaped to provide a component to be formed therein with a desired profile. The working surface 110 includes one or more raised or indented portions, configured to provide the shape of the component to be formed therein.
The working surface 110 is coated with an oxide layer 101 for wear resistance and to prevent the formed part from sticking to the die surface, for example as shown in the enlarged section view of FIG. 1. The system 100 may include a top cover 112 that seals against the die 102 at a seal bead 114. In one example, the seal bead 114 includes a seal or gasket for improved sealing of the top cover 112 to the die 102. In another example, the seal bead 114 is formed on the die 102 and the cover is sealed to the die using an adhesive, mechanical means, such as a clamp, or other sealing devices such as a hydraulic press that allow the component forming system to function as described herein. When the top cover 112 is sealed to the die 102, a forming chamber 116 is defined as a space between the top cover 112 and die working surface 110.
The gas inlet 108, formed for example in the top cover 112, is in flow communication with the forming chamber 116. A supply of pressurized gas (not shown) is provided to the forming chamber 116 through the gas inlet 108 to apply a pressure within the forming chamber 116. A gas discharge 118 is in flow communication with the forming chamber 116, and allows gas supplied via the inlet 108 to exit the forming chamber 116.
In operation, the die 102 is first coated with a lubricant 103, such as graphite and/or boron nitride. As used herein, lubricant 103 refers to lubricants that are not paints. Typically, the lubricants are sprayed onto the working surface 110 of the die 102 to form a substantially uniform layer of lubricant 103. However, other methods of applying the lubricant 103 may be used, such as wiping, dipping, rolling and the like. After the lubricant 103 has been applied to the die, a material stock 120 is placed into die 102. Material stock 120 may be a metal or plastic material to be formed, such as titanium, aluminum, nickel, other metals and metal alloys or combinations thereof. The top cover 112 is closed and the die 102 is heated by a heater (not shown). The die 102 is heated until the material stock 120 reaches a predetermined temperature of approximately between 850 degrees to 1800 degrees Fahrenheit (454° C. to 983° C.), depending on the forming process and material being formed. The die 102 and the cover 112 are placed between the lower platen 104 and the upper platen 106 and a pressure is applied to one or both of the platens.
The heated material stock 120 is then biased against the working surface 110 by pressure exerted by the pressurized gas supplied through the inlet 108. The pressure is applied to the material stock 120 until the material stock takes the shape of the working surface 110, and a component 122 is formed. The formed component 122 is then removed from the die 102. The above described forming procedure may be performed one or more times before spent lubricant is removed and new lubricant is applied to the die. Alternatively, it may be necessary to remove old lubricant 103 and apply a new layer of lubricant to the die 102 after each component 122 is formed and removed from the die.